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# coding=utf-8
# Copyright 2023 The HuggingFace Inc. team.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
""" PyTorch - Flax general utilities."""
from pickle import UnpicklingError
import jax
import jax.numpy as jnp
import numpy as np
from flax.serialization import from_bytes
from flax.traverse_util import flatten_dict
from ..utils import logging
logger = logging.get_logger(__name__)
#####################
# Flax => PyTorch #
#####################
# from https://github.com/huggingface/transformers/blob/main/src/transformers/modeling_flax_pytorch_utils.py#L224-L352
def load_flax_checkpoint_in_pytorch_model(pt_model, model_file):
try:
with open(model_file, "rb") as flax_state_f:
flax_state = from_bytes(None, flax_state_f.read())
except UnpicklingError as e:
try:
with open(model_file) as f:
if f.read().startswith("version"):
raise OSError(
"You seem to have cloned a repository without having git-lfs installed. Please"
" install git-lfs and run `git lfs install` followed by `git lfs pull` in the"
" folder you cloned."
)
else:
raise ValueError from e
except (UnicodeDecodeError, ValueError):
raise EnvironmentError(f"Unable to convert {model_file} to Flax deserializable object. ")
return load_flax_weights_in_pytorch_model(pt_model, flax_state)
def load_flax_weights_in_pytorch_model(pt_model, flax_state):
"""Load flax checkpoints in a PyTorch model"""
try:
import torch # noqa: F401
except ImportError:
logger.error(
"Loading Flax weights in PyTorch requires both PyTorch and Flax to be installed. Please see"
" https://pytorch.org/ and https://flax.readthedocs.io/en/latest/installation.html for installation"
" instructions."
)
raise
# check if we have bf16 weights
is_type_bf16 = flatten_dict(jax.tree_util.tree_map(lambda x: x.dtype == jnp.bfloat16, flax_state)).values()
if any(is_type_bf16):
# convert all weights to fp32 if they are bf16 since torch.from_numpy can-not handle bf16
# and bf16 is not fully supported in PT yet.
logger.warning(
"Found ``bfloat16`` weights in Flax model. Casting all ``bfloat16`` weights to ``float32`` "
"before loading those in PyTorch model."
)
flax_state = jax.tree_util.tree_map(
lambda params: params.astype(np.float32) if params.dtype == jnp.bfloat16 else params, flax_state
)
pt_model.base_model_prefix = ""
flax_state_dict = flatten_dict(flax_state, sep=".")
pt_model_dict = pt_model.state_dict()
# keep track of unexpected & missing keys
unexpected_keys = []
missing_keys = set(pt_model_dict.keys())
for flax_key_tuple, flax_tensor in flax_state_dict.items():
flax_key_tuple_array = flax_key_tuple.split(".")
if flax_key_tuple_array[-1] == "kernel" and flax_tensor.ndim == 4:
flax_key_tuple_array = flax_key_tuple_array[:-1] + ["weight"]
flax_tensor = jnp.transpose(flax_tensor, (3, 2, 0, 1))
elif flax_key_tuple_array[-1] == "kernel":
flax_key_tuple_array = flax_key_tuple_array[:-1] + ["weight"]
flax_tensor = flax_tensor.T
elif flax_key_tuple_array[-1] == "scale":
flax_key_tuple_array = flax_key_tuple_array[:-1] + ["weight"]
if "time_embedding" not in flax_key_tuple_array:
for i, flax_key_tuple_string in enumerate(flax_key_tuple_array):
flax_key_tuple_array[i] = (
flax_key_tuple_string.replace("_0", ".0")
.replace("_1", ".1")
.replace("_2", ".2")
.replace("_3", ".3")
.replace("_4", ".4")
.replace("_5", ".5")
.replace("_6", ".6")
.replace("_7", ".7")
.replace("_8", ".8")
.replace("_9", ".9")
)
flax_key = ".".join(flax_key_tuple_array)
if flax_key in pt_model_dict:
if flax_tensor.shape != pt_model_dict[flax_key].shape:
raise ValueError(
f"Flax checkpoint seems to be incorrect. Weight {flax_key_tuple} was expected "
f"to be of shape {pt_model_dict[flax_key].shape}, but is {flax_tensor.shape}."
)
else:
# add weight to pytorch dict
flax_tensor = np.asarray(flax_tensor) if not isinstance(flax_tensor, np.ndarray) else flax_tensor
pt_model_dict[flax_key] = torch.from_numpy(flax_tensor)
# remove from missing keys
missing_keys.remove(flax_key)
else:
# weight is not expected by PyTorch model
unexpected_keys.append(flax_key)
pt_model.load_state_dict(pt_model_dict)
# re-transform missing_keys to list
missing_keys = list(missing_keys)
if len(unexpected_keys) > 0:
logger.warning(
"Some weights of the Flax model were not used when initializing the PyTorch model"
f" {pt_model.__class__.__name__}: {unexpected_keys}\n- This IS expected if you are initializing"
f" {pt_model.__class__.__name__} from a Flax model trained on another task or with another architecture"
" (e.g. initializing a BertForSequenceClassification model from a FlaxBertForPreTraining model).\n- This"
f" IS NOT expected if you are initializing {pt_model.__class__.__name__} from a Flax model that you expect"
" to be exactly identical (e.g. initializing a BertForSequenceClassification model from a"
" FlaxBertForSequenceClassification model)."
)
if len(missing_keys) > 0:
logger.warning(
f"Some weights of {pt_model.__class__.__name__} were not initialized from the Flax model and are newly"
f" initialized: {missing_keys}\nYou should probably TRAIN this model on a down-stream task to be able to"
" use it for predictions and inference."
)
return pt_model